Birds don't know about or understand glass and it kills' a lot of them. Even birds that fly away after a window collision, may later die due to the effects of a concussion.
Preventing Bird deaths from window hits is quite possible. We know what to do because
Above is a PDF from the Acopian Center detailing
Nine Bird-window Collision Deterrent Methods
and Relative Costs*
Which you can read and/or download if you wish.
*Rough estimates; highly variable because of window sizes and configuration. We used a 36” high x 48” wide window for our calculations.
Note: To work well treatments must be on the outside! a Simple hawk silhouette Won't work!